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XY Ursae Majoris is a short period binary star system in the northern circumpolar constellation of Ursa Major. It is an eclipsing binary with a baseline apparent visual magnitude of 9.50.[3] The system is located at a distance of 221.5 light years from the Sun based on parallax measurements,[2] but is drifting closer with a radial velocity of −10 km/s.[6] It has a relatively high proper motion, traversing the celestial sphere at the angular rate of 0.191″·yr−1.[10]

XY Ursae Majoris

A light curve for XY Ursae Majoris, plotted from TESS data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 09h 09m 55.935s[2]
Declination +54° 29 17.72[2]
Apparent magnitude (V) 9.50[3]
Characteristics
Evolutionary stage Main sequence
Spectral type G2V + K5V[4]
B−V color index 0.765±0.039[3]
Variable type Detached eclipsing binary, RS CVn[5]
Astrometry
Radial velocity (Rv)−9.98±0.83[6] km/s
Proper motion (μ) RA: −49.781 mas/yr[2]
Dec.: −182.641 mas/yr[2]
Parallax (π)14.7223 ± 0.0137 mas[2]
Distance221.5 ± 0.2 ly
(67.92 ± 0.06 pc)
Absolute magnitude (MV)5.41[3]
Orbit[7]
Period (P)0.4789961 d
Semi-major axis (a)3.05±0.01 R[8]
Eccentricity (e)0.0
Inclination (i)79.81[8]°
Periastron epoch (T)2,453,821.6344±0.0002
Semi-amplitude (K1)
(primary)
124.74±0.28 km/s
Details
Primary
Mass1.01±0.01[8] M
Radius1.22±0.01[8] R
Luminosity1.10±0.02[8] L
Temperature5,780[4] K
Secondary
Mass0.65±0.01[8] M
Radius0.58±0.01[8] R
Luminosity0.09±0.01[8] L
Temperature3,850[4] K
Other designations
XY UMa, AG+54 702, BD+55 1317, HD 237786, HIP 44998, SAO 27143, PPM 32024[9]
Database references
SIMBADdata

The variability of this system was discovered by W. Strohmeier and its period was determined by R. Kippenhahn, with the findings announced in 1955.[11] It was found to be a detached eclipsing binary system, and by 1963 a variable primary component had been noted.[12] E. H. Geyer made intermittent light curve studies of the system starting with its discovery up until 1975,[11] ascribing variability in the light curve to star spot activity on the primary component. The orbital period of the pair was determined to be 0.479 d,[13] with the orbital plane inclined at an angle of 79.84° to the line of sight from the Earth.[8]

By 1990, enough data had been collected to identify a long term variation of the period, and it was hypothesized this was caused by a third body in the system orbiting the close binary.[14] The orbital period of this component was estimated to be ~30 years in 2001,[15] then refined to 26.7 years by 2010. If the orbital plane of this component is the same as the inner pair, its mass would be 18% of the mass of the Sun. An alternative solution to the period change suggests magnetic activity causes shifts in the angular momentum of the system, but this is considered less likely.[8]

This is a double-lined spectroscopic binary star system with an orbital period of 11.5 h.[7] The primary component is a G-type main-sequence star with a stellar classification of G2V.[4] It is an RS Canum Venaticorum-type variable that is magnetically active[5] and a bright X-ray source.[16] Despite this, relatively few optical flares have been observed.[16] The cooler secondary is a K-type main-sequence star of class K5V that is smaller and less massive than the primary.[4]


References


  1. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  2. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  4. Lister, T. A.; et al. (October 2001), "Starspot distributions on XY UMa during 1997-2000 from eclipse mapping", Monthly Notices of the Royal Astronomical Society, 326 (4): 1489–1498, Bibcode:2001MNRAS.326.1489L, doi:10.1111/j.1365-2966.2001.04712.x.
  5. Samus', N. N; et al. (2017), "General catalogue of variable stars", Astronomy Reports, GCVS 5.1, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. Karataș, Yüksel; et al. (2004), "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution", Monthly Notices of the Royal Astronomical Society, 349 (3): 1069–1092, arXiv:astro-ph/0404219, Bibcode:2004MNRAS.349.1069K, doi:10.1111/j.1365-2966.2004.07588.x, S2CID 15290475.
  7. Pribulla, Theodor; et al. (May 2007), "Radial Velocity Studies of Close Binary Stars. XII", The Astronomical Journal, 133 (5): 1977–1987, arXiv:astro-ph/0611875, Bibcode:2007AJ....133.1977P, doi:10.1086/512772.
  8. Yuan, Jinzhao (May 2010), "Period Variation and Asymmetry Light Curves of XY Ursae Majoris", The Astronomical Journal, 139 (5): 1801–1807, Bibcode:2010AJ....139.1801Y, doi:10.1088/0004-6256/139/5/1801.
  9. "XY UMa", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-03-03.
  10. Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854, S2CID 2603568.
  11. Geyer, E. H. (1976), Eggleton, P.; et al. (eds.), "Starspot Activities as an Interpretation for the Light Curve Changes of the Close Binary Star XY UMA", Structure and Evolution of Close Binary Systems; Proceedings of the Symposium, Cambridge, England, July 28-August 1, 1975, Dordrecht: D. Reidel Publishing Co., no. 73, p. 313, Bibcode:1976IAUS...73..313G. Symposium sponsored by the International Astronomical Union.{{citation}}: CS1 maint: postscript (link)
  12. Lorenzi, L.; Scaltriti, F. (1977), "The variable light-curve of the eclipsing binary XY UMa", Acta Astronomica, 27: 273–279, Bibcode:1977AcA....27..273L.
  13. Geyer, E. H. (May 1977), "Remarks on Erratic Period Fluctuations of Detached Close Binaries and the Constancy of the Orbital Period of XY UMa", Astrophysics and Space Science, 48 (1): 137–144, Bibcode:1977Ap&SS..48..137G, doi:10.1007/BF00643045.
  14. Pojmanski, G.; Geyer, E. H. (1990), "The period behaviour of the spotted binary XY UMa", Acta Astronomica, 40: 245, Bibcode:1990AcA....40..245P.
  15. Pribulla, T.; et al. (June 2001), "An active binary XY UMa revisited", Astronomy and Astrophysics, 371: 997–1011, Bibcode:2001A&A...371..997P, doi:10.1051/0004-6361:20010459.
  16. Gong, Hang; et al. (August 2016), "Three X-ray flares near primary eclipse of the RS CVn binary XY UMa", Research in Astronomy and Astrophysics, 16 (8), arXiv:1605.09262, Bibcode:2016RAA....16..131G, doi:10.1088/1674-4527/16/8/131, 131.

Further reading



На других языках


- [en] XY Ursae Majoris

[ru] XY Большой Медведицы

XY Большой Медведицы (лат. XY Ursae Majoris), HD 237786 — двойная затменная переменная звезда типа Беты Лиры (EB) в созвездии Большой Медведицы на расстоянии приблизительно 223 световых лет (около 68 парсеков) от Солнца. Видимая звёздная величина звезды — от +10,17m до +9,5m[7]. Орбитальный период — около 0,479 суток (11,496 часов).



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